In recent years the trend in the telephone apparatus and systems has been toward increased computerization. As a result many such systems of modern design contain data processing sub-systems to perform supervision and control functions in lieu of the hitherto extensively used electromechanical devices.
The requirements placed on telephone systems are in certain aspects sometimes in conflict with the performance specifications of conventional data processing systems. Certainly the most prominent example of such conflict arises due to the extreme reliability requirements placed on telephone systems and apparatus. In contrast, occasional failure of a computer, be it because of hard or software malfunction, is not uncommon.
While often higher reliability on telephone systems is attained by duplicating critical units of the system, such approach is in conflict with yet another import requirement, that of cost.
The present invention discloses a method for inexpensively providing spare memory capability in a data processing system at the cost of slightly reducing its normal functional capability. The present invention is particularly suitable for use in certain types of telephone systems. It is, however, not restricted to such use, as will be apparent to those skilled in related arts.